Frequent occurrence of triclosan hydroxylation in mammals: A combined theoretical and experimental investigation

• Published in: Journal of hazardous materials Vol. 407; p. 124803
• Main Authors: Zhang, Hongna, Sanidad, Katherine Z., Zhu, Lin, Parsonnet, Julie, Haggerty, Thomas D., Zhang, Guodong, Cai, Zongwei
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 05.04.2021
• Subjects: aerobiosis; androstanes; anti-infective agents; bile; chlorine; CYPs; cytochrome P-450; enzymes; feces; humans; hydroxylation; in Silico; in Vitro; in Vivo; liver; mass spectrometry; metabolites; mice; oxidation; Oxidative metabolism; Triclosan; urine; in Vivo; in Vitro; Triclosan; in Silico; Oxidative metabolism; CYPs
• ISSN: 0304-3894; 1873-3336; 1873-3336
• DOI: 10.1016/j.jhazmat.2020.124803

Triclosan (TCS) is a widespread antimicrobial agent with many adverse health risks. Its hepatoxicity invariably points to the activation of constitutive androstane receptor (CAR), which regulates cytochrome P450 (CYP) genes that are critical for oxidative metabolism. Here, we provide the theoretical and experimental evidences showing that metabolic activation of TCS frequently occurs through aromatic hydroxylation in mammals. CYP-mediated oxidation was predicted to take place at each aromatic C‒H bond. Molecular docking and in vitro approaches reveal oxidative reaction could be efficiently catalyzed by CAR-regulated CYP2B6 enzyme. Parallel reaction monitoring (PRM) high-resolution mass spectrometry was utilized to identify and profile TCS oxidative metabolites in paired mouse liver, bile, feces, plasma and urine. We found multiple hydroxylated isomers including the products generated via the NIH shift of chlorine, as well as their subsequent conjugates. These metabolites showed isomer-specific retention in mice. Glucuronide conjugates are more readily excreted than the sulfates. Moreover, for the first time, isomeric hydroxylated metabolites were detected in the urine and stool of human subjects used TCS-contained household and personal care products. Collectively, these findings suggest that hydroxylation is an important, yet often underestimated element that worth considering to fully evaluate the biological fates and health risks of TCS. [Display omitted] •TCS could be efficiently catalyzed by CYP enzymes through theoretical calculations.•Multiple hydroxylated isomers of TCS were identified in mice using PRM-based HRMS.•Excretions of hydroxylated metabolites are isomer-specific and conjugate-selective.•TCS hydroxylated metabolites were detected in human samples for the first time.•Metabolic activation of TCS frequently occurs, yet often underestimated in mammals.